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NEW ORLEANS (AP) – Prospects for roses grown in the United States are becoming a little less encouraging, with the spread of an incurable virus that causes major damage to the rose branch of $ 250 million a year.
American rose growers make up the bulk of this activity and face a growing challenge from pink rosette disease, which can kill roses in three years. Its many symptoms include super-spiny stems and clusters of stems called rosettes or witches brooms.
A producer spent $ 1 million to get rid of rose rosette disease and some small nurseries had to destroy 10,000 plants, said Dr. David Byrne of Texas A & M University, responsible for a 4-year project. , $ 6 million to study the virus and find varieties of resistant roses.
"It moves very easily and it's hard to detect initially – it's really scary for someone in the production," Byrne said. "If the pots arrive in their production areas, they must eliminate thousands of plants, even then they do not know if they have gotten rid of them."
He also said, "I think we see it in more areas than 10 years ago."
The virus, spread by wind-blown mites about half the length of a grain of salt, has been found in at least 30 states. In Texas, the Fort Worth Botanical Garden had to replace the entire collection of roses. The virus has recently spread to northwestern Louisiana, including the hometown of the American Rose Society and its gardens, the largest US park devoted to the national flower.
The rose rosette has been known since the early 1940s and has been hailed as a possible way to eradicate an invasive plant.
The disease has been identified for the first time on wild multiflora roses in California, the Rocky Mountains and Manitoba, Canada. In the 1990s and even in the early 2000s, scientists considered that it was a way to control these invasive plants.
It has been recognized as a problem for roses grown only in the last decade, said Byrne.
This is the latest blow to the company. South American competition has forced most US producers to leave the cut flower market in recent decades. This market grew from $ 200 million in 1990 to $ 22 million in 2015.
This virus threatens the rose bush trade, estimated at more than $ 200 million in 2015. It seems to be a growing problem as more and more cultivated roses are used in landscapes, according to a website created by a coalition of rose growers and scientists.
In Louisiana, where rose rosette disease was first detected in 2015, it is spreading at an alarming rate in the commercial and residential plantations of Bossier City and Shreveport, where the American Rose Center is located. . plant pathologist.
The 40 acres (16.2 hectares) with rose gardens in the center are free of the disease, said the company's executive director, Laura Seabaugh.
According to experts, unless you remove an infected shrub, mites will spread the virus throughout a garden and beyond.
It can mean tough choices, said Dr. Mark T. Windham, who tests plants at the University of Tennessee-Knoxville to find resistant varieties.
"People have said to me:" The bush that has it, it's the only clone of the rose of my great-grandmother who survived. "I hate to say it, but are you going to try to save that rose and jeopardize your 500-bush rose garden?" He said.
The Fort Worth Botanical Garden uprooted approximately 2,000 bushes in 2015, said Rosarist Jeffrey Myers. He said that their tight rows let the mites "sneak through like a pink-rose highway". The botanical garden currently has about 350 roses, separated by at least 3 to 4 feet (1 to 1.3 meters), with other plants as roadblocks.
Byrne says some large landscapers do not use roses because their maintenance is too expensive.
Customers still want them, but will not pay to replace the infected plants, said Joe Ketterer, in the Ruppert landscape in Laytonsville, Maryland, which works in six states and in the District of Columbia. He said his company used roses, but the affected branches were diluted, using hormones to stimulate growth in parts of the same plant without symptoms.
In Tennessee-Knoxville, the University of Delaware and the state of Oklahoma, researchers have found infected, mite-infested twigs in the foliage of healthy plants to see which ones are staying well.
"Up to now, we have 20 roses that look good.It's their fourth year," said Windham. But their test will not be completed until it has lasted four years without infection, he said.
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